Tyre tread

Abstract: A tyre tread for pneumatic vehicle tyres comprising tread blocks (7) of a central block row (3) separated from one another by inclined grooves (6) which consist of two angularly extending groove sections (9,10) which meet at the central circumferential plane (8). Furthermore, two circumferential grooves (4,5) extend at an acute angle to the circumferential plane of the tyre in the region of the blocks (7,17) which bound them at the sides.

Description: The invention relates to a tyre tread for pneumatic vehicle tyres comprising a central row of blocks, extending in the circumferential direction of the tyre and rows of blocks located in the shoulder regions separated from the central row by circumferential grooves. Tyre treads according to the preamble of claim 1 are known for example from EP-A-0485883 and EP-A-0485778. Known patterns of this kind frequently have the disadvantage that the aqua-planing behaviour and the winter characteristics leave something to be desired. The object of the invention is accordingly to provide a tread for pneumatic vehicle tyres which have both an improved aqua-planing behaviour and also improved winter characteristics. According to one aspect of the invention a tyre tread for pneumatic vehicle tyres comprises a central row of blocks extending in the direction of the tyre circumference and rows of blocks located in the shoulder regions and separated from the central row by circumferential grooves, wherein the tread blocks of the central row are mutually separated by inclined grooves which comprise two groove sections extending at an angle to and meeting each other at the central circumferential plane, and in that the two circumferential grooves extend at an acute angle to the tyre circumferential plane in the region of the blocks which they bound laterally, characterised in that the blocks of the row of blocks located in the shoulder are mutually separated by substantially straight transverse grooves, said grooves extending at an angle of 65° to 85° with respect to the central circumferential plane of the tyre. As a result of the invention a block profile having a specified direction of running is provided, with both good aqua-planing performance and good winter characteristics, in particular the traction in snow and the braking characteristics are substantially improved through the special layout of the inclined and circumferential grooves, and thus of the shaped blocks. The two angularly extending inclined grooved which meet at the central circumferential plane can be arranged such that they lie ideally in the outflow direction of the water, with the water being led away to both sides from the central circumferential plane. The circumferential grooves which extend regionally at an acute angle to the circumferential plane of the tyre, i.e. to the central circumferential plane, or to a plane parallel hereto, provide for good ejection of snow and self-cleaning characteristics of the vehicle tyre. The groove sections of the two inclined grooves are preferably arranged at the same angle with respect to the central circumferential plane, in particular at an angle of approximately 50°. The alignment of the two groove sections is hereby symmetrical to the central circumferential plane. Furthermore, very favourable driving characteristics can be achieved on wet and wintry road when the two groove sections of the inclined grooves are slightly curved. In accordance with a particularly preferred embodiment, the inclined grooves widen towards the circumferential grooves, with the boundary walls of the inclined grooves mutually enclosing an angle of preferably 10°. In this way, particularly good water drainage is ensured towards the circumferential grooves, which are made correspondingly broad. The side edges of the blocks arranged in the shoulder regions are advantageously arranged at a larger acute angle to the circumferential plane of the tyre than the side edges of the blocks of the central row of blocks. In this way the peripheral grooves broaden in a direction opposite to the direction of running in the region of the lateral blocks which bound it, whereby the ejection of snow and the self-cleaning effect of the tyre are further improved. Particularly good aqua-planing characteristics are furthermore achieved when, in accordance with a particular embodiment, the blocks located in the shoulder regions are mutually separated by substantially straight transverse grooves which essentially have the same width as the inclined grooves close to the circumferential grooves and which extend at an angle of approximately 75° to the circumferential plane of the tyre. It is furthermore advantageous when, in accordance with a further embodiment of the invention, a relatively high number of blocks, preferably 60-64 blocks,, depending on the tyre diameter, are distributed around the tyre circumference for each row of blocks. In this way a large number of transverse edges are provided which has the consequence of good traction in snow and increased braking grip effect. The increased number of inclined and transverse grooves improves furthermore the drainage effect and thus the aqua-planing behaviour. The blocks in the shoulder region are preferably arranged displaced in the circumferential direction relative to the blocks of the central row of blocks. A design of this kind leads in particular to a reduction of running noise and to an improvement in the running stability on a dry road. In accordance with a further embodiment the blocks have a plurality of sipes arranged perpendicular to the direction of running. In this way the traction and the braking effect in snow are in particular improved. Furthermore, positive influences on the lateral stability and steering effect also results because slippage sets in later. At the same time, the lateral stability of the profile blocks is maintained as a result of the perpendicular arrangement of the sipes, which also has a positive effect on the driving behaviour, and in particular on the steering characteristics. In accordance with a further advantageous embodiment of the invention, the sipes are formed with the maximum pattern depth and only have smaller depths at the edges of a block. A design of this kind improves the opening of the sipes and hereby leads to elevated traction in snow and also to an improved self-cleaning of the pattern. Further aspects of the invention will be apparent from the following description of an embodiment in conjunction with the attached Figure which shows a schematic partial plan view of a tread layout in accordance with the invention. Between two circumferentially extending rows of blocks 1,2 in the shoulder regions of the vehicle tyre, there is located a central row of blocks 3 which likewise extends in the circumferential direction of the tyre and is separated from the shoulder row of blocks 1,2 by circumferential grooves 4,5. The central row 3 is subdivided by inclined grooves 6 into individual tread blocks 7 which are arranged centrally to the central circumferential plane 8. The inclined grooves 6 consist of groove sections 9,10 which extend at an angle to one another and meet at the central circumferential plane 8. These groove sections 9,10 respectively extend at an angle of approximately 50° to the central circumferential plane 8 and are aligned in such a way that the point at which they open into each other points forwards in the direction of running of the tyre. The direction of running of the tyre is shown and made clear by the arrow 11. Furthermore, the groove sections 9,10 are slightly curved, with the concave side facing forwards in the direction of running. In order to improve water drainage, the groove sections 9,10 broaden towards the circumferential grooves 4,5 with the boundary walls of each grooves section 9,10 including an angle with one another of approximately 10°. The groove section 10 illustrated in the drawing is extended beyond the groove section 9 by means of a groove extension section 12 of the same width which extends through approximately half of the tread block 7. Starting from this groove extension section 12 a connecting groove 13 of smaller width continue in its longitudinal direction up to the inclined groove which follows in the direction of running. The groove section 9 which extends at an angle to the groove section 10m has in turn a groove extension 14 in the vicinity of the circumferential groove, with the groove extension 14 branching off at right angles from the groove section 9 and extending towards the rear inclined groove in the direction of running, through approximately half the tread block 7. Starting from this groove extension 14, a connecting groove 15 of lesser width is continued in its longitudinal direction up to the rear inclined groove in the direction of running. The widths of the groove extension 14 and of the groove extension section 12 are substantially the same and amount to approximately 30% of the width of the tread blocks 7 measured perpendicularly to the groove section 9 or 10. The width of the groove sections 9 or 10 in the vicinity of the central circumferential plane 8 likewise amounts to approximately 30% of the width of the tread blocks 7. The central row 3 consists of two kinds of tread blocks 7 which are distinguished in that, for the first kind, the groove extension section 12 and the connecting groove 13 extend into the left half of the tread blocks 7 with respect to the central circumferential plane, whereas in the second kind the groove extension section 12 and the connecting section 13 are located to the right of the central circumferential plane 8. Furthermore, with the first kind of tread blocks 7, the groove extension 14 and the connecting groove 15 are arranged on the right-hand side of the central circumferential plane, whereas, with the second kind of profile blocks 7 these lie on the left-hand side of the central circumferential plane 8. In the circumferential direction of the tyre, the two types of tread blocks alternate, so that in each case the next but one tread block is identical. Apart from the arrangement of the groove extension section 12, the groove projection 14 and the connecting grooves 13,15, the tread blocks 7 are, however, identical and have an arrow-shaped form as a result of the inclined grooves 9, the tip of which points in the direction of running. The rows of blocks 1,2 in the shoulder regions are subdivided by transverse grooves 16 into individual tread blocks 17 which are arranged symmetrically with respect to the central circumferential plane 8. The transverse grooves 16 extend substantially in a straight line from the circumferential grooves 4,5 to the lateral edge regions of the tyre and have a width which corresponds approximately to the width of the inclined grooves 6 in the vicinity of the circumferential grooves 4,5. Furthermore, the transverse groove 16 extend at an angle of approximately 75° to the circumferential plane of the tyre. The number of lateral tread blocks 17 is identical to the number of the central blocks 7 and amounts, depending on the tyre diameter, to approximately 60-64 tread blocks. An improvement of the quietness of running is achieved because the lateral profile blocks 17 are not arranged in the circumferential direction of the tyre at the same position as the neighbouring regions of the central tread blocks 7, but are displaced somewhat rearwardly relative to the latter - as seen in the direction of running. This displacement or offset is so dimensioned that the lateral edges 18 of the central profile blocks 7 bounding the circumferential grooves 4,5 and the lateral edges 19 of the lateral profile blocks 17 bounding the circumferential grooves 4,5 on the other side overlap over approximately 50% of their length, as seen in the circumferential direction of the tyre. The circumferential grooves 4,5 are characterised in that the side edges 18 of the central profile blocks 7 and the side edges 19 of the lateral profile blocks 17 do not extend parallel to but rather at an acute angle to the central circumferential plane 8. This angle amounts for the side edges 18 of the central profile blocks 7 to approximately 6°, whereas the angle between the side edges 19 and the central circumferential plane 8 amounts to approximately 10°. The side edges 18,19, which in other respects are straight, thus diverge - as seen in the running direction of the tyre - rearwardly, which makes possible a particularly good discharge of water. As a result of this arrangement, of the transverse edges of two adjacent tread blocks 17 which bound the transverse grooves 16, the transverse edge of which lies to the rear as viewed in the direction of running, projects somewhat further in the direction of the central circumferential plane 8 than the transverse edge adjacent hereto, so that water which is running rearwardly along the side edge 19 is partly directed by the further projecting transverse edge into the transverse groove 16. Sipes 20 arranged perpendicularly to the direction of running are formed both in the central tread blocks 7 and also in the lateral tread blocks 17. At least five of these sipes 20 are provided for each block 7,17. They extend up to the maximum depth of the profile and merely have a lesser depth at the edge of each block 7,17 in order to increase the stability of the blocks in their marginal regions. The arrangement and the depth of the sipes 20 enable an improvement of the traction in snow, an improved braking action and also an improved self-cleaning of the tread, with the lateral stability of the tread blocks simultaneously being retained.

Claims: A tyre tread for pneumatic vehicle tyres comprising a central row (3) of blocks (7) extending in the direction of the tyre circumference and rows (1,2) of blocks (17) located in the shoulder regions and separated from the central row by circumferential grooves, wherein the tread blocks (7) of the central row (3) are mutually separated by inclined grooves (6) which comprise two groove sections (9,10) extending at an angle to and meeting each other at the central circumferential plane (8), and in that the two circumferential grooves (4,5) extend at an acute angle to the tyre circumferential plane in the region of the blocks (7,17) which they bound laterally, characterised in that the blocks (17) of the row (1,2) of blocks located in the shoulder are mutually separated by substantially straight transverse grooves (16), said grooves (16) extending at an angle of 65° to 85° with respect to the central circumferential plane (8) of the tyre. A tread according to claim 1, characterised in that the two groove sections (9,10) of the inclined grooves (6) are arranged at the same angle with respect to the central circumferential plane (8), said angle being in the range of 40° to 60°. A tread according to claim 2, characterised in that the two groove sections (9,10) are arranged at an angle of 50°. A tread according to either of claims 2 or 3, characterised in that the two groove sections (9,10) are slightly curved. A tread according to any of claims 1 to 4, characterised in that the inclined grooves (6) widen towards the circumferential grooves (4,5), with the boundary walls of the inclined grooves (6) mutually enclosing an angle of 5° to 15°. A tread according to claim 5, characterised in that the boundary walls of the inclined grooves (6) mutually enclose an angle of 10°. A tread according to any one of the preceding claims, characterised in that a groove section (9 or 10) of each inclined groove (6) is extended beyond the other groove section (10 or 9) which extends at an angle thereto, by means of a groove extension section (12). A tread according to claim 7, characterised in that the groove extension section (12) extends through half of the block (7). A tread according to either of claims 7 or 8, characterised in that the groove extension sections (12) of the inclined grooves (6) alternatively extend from the central circumferential plane (8) toward the one side or the other side of the central circumferential plane (8). A tread according to any of claims 7 to 9, characterised in that a connection groove (13) narrower than the groove extension section (12) extends from and in continuation of the groove extension section (122), in the longitudinal direction thereof, up to the inclined groove (6) which follows in the direction of running. A tread according to any one of the preceding claims, characterised in that a groove extension (14) branches off from one groove section (9) of an inclined groove (6), with the groove extension (14) having the same width as and extending preferably perpendicular to this groove section in the direction of the inclined groove (6) located to the rear in the direction of running. A tread according to claim 11, characterised in that the groove extension (14) extends through half of the profile block (7). A tread according to either of claims 11 or 12, characterised in that a connection groove (15) narrower than the groove extension (14) extends from and in continuation of the groove extension (14) in the longitudinal direction thereof up to the inclined groove (6) located to the rear in the direction of running. A tread according to any of claims 10 to 12, characterised in that the width of the connection grooves (13,15) amounts to 30% to 70% of the average width of the inclined grooves (6). A tread according to claim 14, characterised in that the width of the connection grooves is 50% of the average width of the inclined grooves (6). A tread according to any one of the preceding claims, characterised in that, proceeding in the tyre circumferential direction, every second block (7) of the central row of blocks (3) is geometrically similar. A tread according to any one of the preceding claims, characterised in that the side edges (19) of the profile blocks (17) located in the shoulder region which limit the circumferential grooves (4,5) are arranged with respect to the tyre circumferential plane at a greater acute angle than the side edges (18) of the profile blocks (7) of the central row of blocks (3), such that the circumferential grooves (4,5) widen in the direction opposite to the direction of running of the tyre in the region of the profile blocks (7,17) which laterally limit the circumferential groove (4,5). A tread according to claim 17, characterised in that the side edges (19) of the profile blocks (17) located in the shoulder region, which limit the circumferential grooves (4,5) are arranged with respect to the tyre circumferential plane at an angle of 5° to 15° and in that the side edges (18) of the profiled blocks (7) of the central row of blocks (3) are arranged with respect to the circumferential plane of the tyre at an angle of 2° to 10°. A tread according to claim 18, characterised in that the side edges (19) of the blocks (17) of the shoulder region are at an angle of 10°. A tread according to either of claims 18 or 19, characterised in that the side edges (18) of the blocks (7) of the central row of blocks are at an angle of 6°. A tread according to any one of the preceding claims, characterised in that the substantially straight transverse grooves (16), separating the blocks (17) in the shoulder regions extend at an angle of 75° with respect to the circumferential plane of the tyre. A tread according to any one of the preceding claims, characterised in that the number of profile blocks (17) of the rows of blocks (1,2) located in the shoulder regions is equal to the number of profile blocks (7) of the central row of blocks (3). A tread according to claim 22, characterised in that the number of profile blocks (7) of the central row of blocks (3) is 60 to 64. A tread according to claim 22, characterised in that the number of blocks (7) of the central row of blocks (3) is 56 to 58. A tread according to any one of the preceding claims, characterised in that the profile blocks (17) of the rows of blocks (1,2) located in the shoulder regions are arranged offset in the tyre circumferential direction with respect to the profile blocks (7) of the central row of blocks (3). A tread according to any one of the preceding claims, characterised in that the profile blocks (17) of the rows of blocks (1,2) located in the shoulder regions are symmetrically arranged with respect to the central circumferential plane (8). A tread according to any one of the preceding claims, characterised in that the profile blocks (7,17) are provided with a plurality of sipes (20), preferably extending perpendicular to the direction of running. A tread according to claim 27, characterised in that the sipes (20) extend perpendicular to the direction of running. A tread according to either of claims 27 or 28, characterised in that the depth of the sipes (20) extend up to the maximum depth of the profile and have a lesser depth only at the edge of a profile block (7,17). A tread according to claim 29, characterised in that the depth of the sipes (20) amounts to 80% of the maximum profile depth. A tread according to claim any of claims 27 to 30, characterised in that the longer sipes have a smaller depth in their central region.

Inventors: KREUZ DIETER, VOIGT KARL GUNTHER, KREUZ, DIETER, VOIGT, KARL GUNTHER
Applicants: SP REIFENWERKE GMBH
Application year: 1994
Main classification: B60C11
IPC codes: B60C11